The present invention relates generally to wear resistance in seals, and more importantly to an improved mechanical seal to improve lubrication and minimize wear and leakage.
Seals, such as axial seals for bushings, are commonly used in endless tracks of track-type earthmoving vehicles and pin joints of many types of heavy equipment, such as hydraulic excavators and wheel loaders. In relatively clean environments, a small amount of inward radial load is required on the sealing lip to seal lubricant within a joint. However, as the operating environment becomes dirtier and more severe, higher lip loads are required to ensure good sealability and to exclude the abrasive contaminants.
Extensive development work has been directed toward improving face seals for protecting the pin joints of an endless track chain. Such track chains operate in extremely abrasive environments under all types of weather conditions. Consequently, the axial face load of the seals must be maintained at a substantial level, for example above about 100 pounds (445 N), while the seals experience a considerable amount of axial motion between the track joint members.
This imposes substantial demands upon the materials that are utilized in the seal, since the seal must not only be sufficiently resilient to follow rapid movements of the joint members over a considerable temperature range, but must also exhibit a substantial wear life in order to retain lubricant within the joint and to exclude dirt.
As previously stated, track-type earthmoving vehicles present a severe environment for the seal. Given the environmental conditions surrounding a typical track-type earthmoving vehicle, abrasive contaminants, such as sand, dirt, rock, and water may enter the gap between the load ring and the bushing. The seal lip must prevent infiltration of the contaminants into the lubricated area. Thus, the seal lip experiences severe conditions, and if the contaminants get lodged under the seal lip, then a groove may be ground into the pin/bushing. Alternatively, the seal lip may finally fail as a result of the abrasion, which will then effectively produce the same groove in the pin/bushing. With a typical smooth contact surface on a seal, a very high axial force must be utilized to prevent the highly abrasive contaminants from being lodged under the seal lip.
Textured features on the contact surface of a seal to decrease the wear rate of mechanical seals caused by exposure to abrasive contaminants and high axial forces were disclosed in a patent application, Ser. No. 08/806,266. The texturing features of that invention were added interior to the outer peripheral edge of the contact surface of the seal. The single row of protrusions acted to break up dirt. Deformation of the protrusions when undergoing pressure placed on the surface of the seal served as fluid wells to introduce lubricant to the contact surface. The textured features included protrusions, protrusions with recesses, indentations, or combinations thereof. The textured features were a single row of protrusions with recesses, indentations, or combinations thereof.
For the most part, the prior art seals have proven only partially satisfactory toward solving the aforementioned problems. Although the single row of textured seals help increase the wear rate of the seal lip, there still exists leakage problems with these seals over time.
In view of the above, it would be advantageous to pro-vide a simple seal assembly having long life expectancy and operational effectiveness over a wide range of deflection in the severe service environment of a track joint or pin joint.
The seal assembly of the present invention is directed to overcome one or more of the problems associated as set forth above.
This invention encompasses the use of textured features on the contact surface of the seal between the inner peripheral edge and the outer peripheral edge. These multiple rows of textured features decrease the wear rate of mechanical seals by providing additional circumferential rows of similar textured features across the entire contact surface of the seal lip.
In another aspect of the invention, an assembly is contemplated, comprising multiple rows of textured features. Multiple rows of textured features are positioned between a first surface having an outer peripheral edge and an inner peripheral edge. A second surface, being substantially flat and pressed against the first surface, produce a seal assembly. In the preferred embodiment, the outer peripheral edge is raised.